This invention relates to methods and devices for improving the performance of hot briquette rolls of the type used for highly reduced iron ore. In particular, the invention is an improvement in hot briquetting machines such as disclosed by Komarek in U.S. Pat. Nos. 3,077,634, 3,269,611, and 3,143,769.
The difficulty in operating hot segmented roll briquette machines has been that the segments must be inserted when they are cold and, of course, relatively contracted. At operating temperatures, i.e., in the range of 900.degree. F, they are fully expanded. The difference in size may be expected to be about 0.03 inch. To achieve uniformity in the hot position of the rolls, they must be spaced with from 0.01 to 0.02 inch between them; the lower portions may be slightly closer together than the outer portions, depending on the shape of the mold segment. Frequently, the abutting mold segments each contain half a mold face, so that a complete briquette is formed half in one and half in the other. In this case, care must be taken that all segments, when they are expanded by the heat, meet precisely so no briquette material will enter the space between mold segments, and form a briquette having a raised portion in the center. Such a seam in the briquette is likely to stick in the mold and render the briquette difficult to dislodge. Uneven briquettes generally are more likely to have weak spots than symmetrical ones.
I am not aware of the use of low-melting alloys as sacrificial shims in the prior art.